Algebra II - Statistics Vocabulary

population

the entire group of individuals about which we want information

sample

the part of the population from which we actually collect information

sample survey

a study that collects data from a sample to learn about the population from which the sample was selected

uses information from a sample to draw conclusions about the entire population

convenience sampling

selects individuals from the population who are easy to reach

bias

an extreme underestimate or extreme overestimate of value you want to know

voluntary response sampling

allows people to choose to be in the sample by responding to a general invitation

random sampling

involves using a chance process to determine which members of a population are included in the sample

simple random sample

chosen in such a way that every group of n individuals in the population has an equal chance to be selected as the samples

sampling without replacement

an individual from a population can be selected only once

sampling with replacement

an individual from a population can be selected more than once

table of random digits

a long string of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 with these properties:

• Each entry in the table is equally likely to be any of the 10 digits 0 through 9

• The entries are independent of each other (knowledge of one part of the table gives no information about any other part)

strata

groups of individuals in a population who share characteristics thought to be associated with the variables being measured in a study

stratified random sampling

selects a sample by choosing an SRS from each stratum and combining the SRSs into one overall sample

cluster

a group of individuals in the population that are located near each other

cluster sampling

selects a sample by randomly choosing clusters and including each member of the selected clusters in the sample

systematic random sampling

selects a sample from an ordered arrangement of the population by randomly selecting one of the first k individuals and choosing every kth individual thereafter

multistage sampling

combines two or more sampling methods

sampling errors

come from the act of choosing a sample

undercoverage

occurs when some members of the population are less likely to be chosen or cannot be chosen in a sample

sampling frame

the list from which the sample is actually chosen

nonresponse

occurs when an individual chosen for the sample can’t be contacted or refuses to participate

response bias

occurs when there is a systematic pattern of inaccurate answers to a survey question

observational study

observes individuals and measures variables of interest but does not attempt to influence the responses

response variable

measures an outcome of a study

explanatory variable

may help explain or predict changes in a response variable

confounding

occurs when two variables are associated in such a way that their effects on a response variable cannot be distinguished from each other

experiment

deliberately imposes treatments (conditions) on individuals to measure their responses

placebo

a treatment that has no active ingredient but is otherwise like other treatments

treatment

a specific condition applied to the individuals in an experiment

experimental unit

the object to which a treatment is randomly assigned

subjects

human experimental units

factor

an explanatory variable that is manipulated and may cause a change in the response variable

levels

the different values of a factor

control group

used to provide a baseline for comparing the effects of other treatments

placebo effect

describes the fact that some subjects in an experiment will respond favorably to any treatment, even an inactive treatment

double-blind

neither the subjects nor those who interact with them and measure the response variable know which treatment a subject is receiving

single-blind

either the subjects or the people who interact with them and measure the response variable don’t know which treatment a subject is receiving

random assignment

means that experimental units are assigned to treatments using a chance process

control

keeping other variables constant for all experimental units

replication

giving each treatment to enough experimental units so that a difference in the effects of the treatments can be distinguished from chance variation due to the random assignment

completely randomized design

the experimental units are assigned to the treatments completely at random

block

a group of experimental units that are known before the experiment to be similar in some way that is expected to affect the response to the treatments

randomized block design

the random assignment of experimental units to treatments is carried out separately within each block

matched pairs design

a common experimental design for comparing two treatments that uses blocks of size 2

sampling variability

refers to the fact that different random samples of the same size from the same population produce different estimates

statistically significant

when the observed results of a study are too unusual to be explained by chance alone